local key = KEYS[1]
local unfollowUserId = ARGV[1]

local exists = redis.call('EXISTS', key)
if exists == 0 then
    return -1
end

local score = redis.call('ZSCORE', key)
if score == false or score == nil then
    return -4
end

redis.call('ZREM', key, unfollowUserId)
return 0